THE TRIGLYCERIDE COMPOSITION, STRUCTURE, AND PRESENCE OF ESTOLIDES IN THE OILS OF LESQUERELLA AND RELATED SPECIES

Members of the genus Lesquerella, native to North America, have oils containing large amounts of hydroxy fatty acids and are under investigation as potential new crops. The triglyceride structure of oils from twenty-five Lesquerella species in the seed collection at our research center has been examined after being hydrolysis-catalyzed by reverse micellar-encapsulated lipase and alcoholysis-catalyzed by immobilized lipase. These reactions, when coupled with supercritical-fluid chromatographic analysis, provide a powerful, labor-saving method for oil triglyceride analysis. A comprehensive analysis of overall fatty acid composition of these oils has been conducted as well. Lesquerella oils (along with oils from two other Brassicaceae: Physaria floribunda and Heliophilia amplexicaulis) have been grouped into five categories: densipolic acid-rich (Class I); auricolic acid-rich (Class,II); lesquerolic acid-rich (Class III); an oil containing a mixture of hydroxy acids (Class IV); and lesquerolic and erucic acid-rich (Class V). The majority of Class I and II triglycerides contain one or two monoestolides at the 1- and 3-glycerol positions and a C-18 polyunsaturated acyl group at the 2-position. Most Class III and IV oil triglycerides contain one or two hydroxy acids at the 1- and 3-positions and C-18 unsaturated acid at the 2-position. A few of the Class III oils have trace amounts of estolides. The Class V oil triglycerides are mostly pentaacyl triglycerides and contain monoestolide and small amounts of diestolide. Our triglyceride structure assignments were supported by H-1 nuclear magnetic resonance data and mass balances.